Intra-operative cardiac resynchronization therapy (CRT) optimization has been demonstrated to significantly improve hemodynamics and will likely improve outcomes of heart failure (HF) patient's undergoing CRT implant. It is believed that patient selection, pacing site, and device timing settings can affect the optimization outcomes.
Currently, the Millar blood pressure sensor is considered as the gold standard for academic related hemodynamic measurement. The Millar blood sensor, however, is invasive and risky. Echocardiography is another approach that is used in clinical practice, but its reliability and accuracy have raised many concerns recently. Echocardiography is also slow and cumbersome when performing a sterile implant. Both the Millar blood pressure sensor and echocardiography have their own technical limitations for CRT application. Therefore, there is no simple and reliable clinical tool for monitoring and optimizing hemodynamics during CRT.
Methods for CRT optimization using photoplethysmography (PPG) have been previously described. U.S. Pat. No. 7,177,686 (Turcott), entitled “Using Photo-Plethysmography to Monitor Autonomic Tone and Performing Pacing Optimization Based on Monitored Autonomic Tone” discloses CRT hemodynamic optimization using a hypothesized stroke volume surrogate, which relates to using amplitude of PPG signal during different pacing intervals. U.S. Pat. No. 6,871,088, entitled “Method and Apparatus for Optimizing Cardiac Resynchronization Therapy” and U.S. Pat. No. 7,548,784, entitled “Method and Apparatus for Optimizing Cardiac Resynchronization Therapy” (both Chinchoy), describe hemodynamic optimization by a cardiac output method, which again uses amplitude features of the PPG signal or a surrogate for blood pressure in order to estimate stroke volume.